Toaster



1952 R. o. STEVENSON mm. 2,616,358

TOASTER 5 Sheets-Sheet 5 Filed Oct. 10, 1947 Aggy FIG. 10.

Inuemors Poberf 0. Sfeuenson & Char/es P. 7Z/rner by fheir Womeys Patented Nov. 4, 1952 22616553., 'I-"OAS'IERL Robert. Stevenson, Philadelphia; and; Charles. R1 u er;- n fie w hiaiM nf m ry.

County, Pa'., a'ssigiiors. to Proctor. Electric Co n pall i ade i h ar aco m ahbn.o f nce sylvania 6 Claims. This, inventionrelates to toasters, and; more. particularly to. automatic toasters having-ther mostatic control means to terminate. the. toasting cycle;

More specifically, this invention contemplates theprovision of an, improved toaster of this character which will produce successive slices; of toasted bread having uniformly. similar color. In toasters ofthis character, having; abreadsuriacfi temperature sensitive thermostat, to terminate the heating; or toastin cycle, provisions; must be made'to. correct. or compensate for, the rise in temperature insidesthe body- Ofbhg toaster-as, successiveslices of toast are made; Intoasters where it, is desirable to produce successive slices oi toast, having similar color v and. texture, it is. important 21. Fig 8. is a sectionalview taken along. line. ofiEigfi.

FigLQl'isa sectional viewtaken along line. 95 1' I of Fig.7..

that the toasting cycle. beterminated. when the surface temperature of the toast has been raised to. the proper browning, orsearing, level When a. thermostat, which; is, to beresponsive to this.

bread surface. temperature is placed inside the body of a toaster it is subjected to extraneous heats. other than that of thezbread. The greatest of these is the generalv airtemperature of the space in which it is; located. Another-isthe radiant heat. from. thetoaster heating elements. It is, therefore, desirable; to provide means for correcting for the eflfectof theseheats on-the flexure of: the thermostatic bimetallic element. whic is; to. be responsive to the temperatureof the bread.

One object of this invention is to p rovide-a con pensa-ted bimetallic thermostat. for electricbread toasting devices which will permit successive slices of. toasted bread to, be producedhavipgsimilar. color.

Other objects andfeatures of the invention will be apparent from the following description.

In the accompanying drawings:

1 is an end elevatiomlviewof a. toaster embodying. the invention, with a portion of thecasing. broken away and with certain elements.-

Fig. 10 is, a perspective view. showing; an end;

plate of thetoaster" and the; mechanism; associ til d h rewith; and

Fig. l l i'sa perspective view illustratingthecone trolling mechanism employed in. con junctib' z'il witl' theswitch.

Re'ferring'first'toFig. 1., there is shown a toaster I: of the type in whichet'wo bread, wells are pro; vided toreceive twosli'cesof. bread. In the'illus; tration, oneof the bread. wellsis shown atlZla'nd a slice. of bread'i's represented in aqeandyaasn outline at 3; As. is customary. in. such toast" each. bread. slice. is supported between; vertical.

wire. elements fljand s which cache. the. bread receiving. well. The bread slice represented isj subjected to h'eat'from the outer heating. element.-

lif and the. inner heating element 1', the latter being common to 'both'offthe breadwells as. is customary. in many toasters of this type. A verticallyj'niov able bread carriage, partly shown at 8;,is adapted. to be lowered'into the position shownjto'support the bread slices and is automatically raised to partiallyejiect the bread slices. at 'thefeiid or the toasting operation, as is also customary. in toast".-

ers; of this; general type. It will be understood; that-the toaster constructionas thus far described.

is of conventional form and requires no further; description. i 4

In accordance with the present invention,.there is provided a novel thermostat-J9. which actuates', a switch l0, as'hereinafter described. The switch It) is connected'in series. with theheatiiig ale; ments so as to control the. energiz'ation thereofj A plate ll serves to support both'the thermostat and the'switch. It'will be seen that the thermo} stat '9 is disposed above the plate ll, whil'elth'e,

switch It] is disposed below the said plate within an. inverted channel" formed" by walls I; turned downfromtheplate l'l'.

Referringto the thermostat 9., as-shown infliigs. 1' to 4. a rigid supporting member [3, secured-to the plate I'l', serves tosupport the elements" of this device. A main bimetallic element (4' has its upper end apertured at ['5' and is loosely sup;

ported by the rigid support l3 whose upper. end. e xt'endsjthrough the aperture ofelementM. The

element I4 is arranged and shaped so as to be.

responsive to the surface temperatureof 'th bread slice 3. As may be seen in Fig. 1, theupp er. por tion of" element I4 is curved outwardly andiex end into the b a l s as i be sflgagd'by the'bread slice, while the lower part of said 'l more uniformly in conjunction with a bread slice 4 from the plate. At the bottom of the hollow body 2|, there are two spaced contact bars 28 and 29 having terminal elements 383 and 3!, which extend to the outside of the switch body and by means of which electrical connection is made to said contact bars. Also at the bottom of the hollow body 2| there is a fulcrum element 32 and a shoulder 33 on which the weight 22' is adapted ,to rest. The fulcrum element 32 is rounded at the top thereof, so that the weight 22 may rock thereabout as hereinafter described. At the bothaving irregular shape or texture. Furthermore, y

it has been found that the thermostatic element in such arrangement is least affected by varia tions in the moisture content of the bread.

At the lower end of the bimetallic element It there is provided a stiff wire extension l5 which is fixedly secured to the element l4 and which extom of the weight there is a contact bridge 34 which is adapted to engage the contact bars 28 and 29. g The upper part of the inset 22a is formed tends downwardly through an opening in the plate ll.

Ill as hereinafter described.

The thermostat 9 further comprises a second bimetallic element I! which is welded, or otherwise securely attached, to the supporting member l3 at 13a. The upper portion of the bimetal element H. is partially flanged at Ila to accommodate the pivot link l8 which has extending hinge pins 26 and hinge pivots I8a. The pivot link I8 is fixediysecured to the bimetallic element ll at its upper end Ila, and is pivotally attached to the element [4 at i8a. The purpose of the bimetal element .l I is to minimize the effects on the main bimetal I4 of the direct heat from the heating element 7 and of the variations and increase in the air temperature within the: casing of the toaster. mentl'i "acts in opposition to the element [4, so that the wire It is subjected to a diiferential action.. The lower end of the element l 4 is deflected toward the' left, as viewed in Fig. 1, in response tolthe' heat received by said element, while the upper portion of element l7 deflects toward the right in response to heat received thereby. Thus, the element ii compensates for the undesired temperature influences to which the main bi-' pins thereon, so that the shield is freely sus--,

pended and does not interfere with the motion of the element H. The bimetal element I7 is enclosed on three sides by the shield l9, and is partially shielded by the support IS on the'fourth side. Thus the element I! is shielded fromthe quick" cooling effect of untoasted bread slices, and at the same time this element is responsive to the temperature influences for which'it is to compensate.

Referring now to the switch IE, this device is illustrated in Figs. 6 to 9 which show it greatly enlarged for the sake of clear illustration. It comprises a hollow body 2i formed of insulating material such as a suitable ceramic material, within which there is loosely disposed a small weight 22 preferably composed of a metal block and'having an inset member 220. of insulating material such as ceramic material. .A thin metallic lid 23 is removably associated with the upper part of the hollow body 2! 'andserves to close the same. Th body 2| is formed with attachment cars 24 and 25 (see Fig. 5) by means ofwhich it is suspended from the plate I I, being secured to bracket elements 25 and 2'! struck-out This rod serves to actuate the switch The arrangement is such that the ele-' to loosely retain the head 35 of a pin 36 which projects to the outside of the hollow body. Thus the head 35 is loosely disposed in a recess or socket 37.

The pin 36 is actuated by the thermostat 9 through the wire [5 and a lever 38 (Fig. 1) which 42, the purpose of which will be seen presently. It will be seen that the switch la is a gravitytype switch, and it is self-closing under the influence of gravity acting on the weight 22. In the absence of any force exerted on the pin 36, the weight is disposed as shown in Figs. 6 and 8, resting on the shoulder 33 and having the contact bridge 34 in engagement with the contact bars 28 and 29. If the lever 38 is free, the switch is permitted to close. As indicated in Fig. 6, the wire I6 is normallyout of engagement with the lever 38 but it moves towards said lever as the bimetal element I4 flexes in response to increasing surface temperature of the associated'bread slice. When the wire 16 has moved sufficiently, it engages the lever 33 and actuates the pin 36 through said lever, as illustrated in Fig. 7, caus-' ing opening of the switch as hereinafter described, the weight 22 rocking about the fulcrum element 32. Thus the switch is opened against the gravi'' tational force acting on the weight 22. The interruption' of the toasting operation causes the bimetal element It to return to its normal position and consequently the wire It moves away from lever 38 as indicated in Fig. 7. The manner in which the toasting operation'is terminated will be described later.

' The gravity-type switch has important operating characteristics which enable it to cooperate with the thermostat 9 to the end that each bread slice will be toasted to the same color. When the switch is first permitted to close with the toaster connected to a source of current, which is during the usual factory test, the contact bridge 34 en'- gages one of the stationary contacts slightly ahead of the other. This is due to the structure of the switch as above described. It causes 'a slight welding of the contacts on the side where they close last, due to the current flowing through the contacts at the point where the circuit is commade weld ontheopposite side remainsintact but is. weakened by the bending action. The condition of the. switch at this time is indicated in broken lines in Fig. 9. When the switch next closes, a fresh weld is formed at the side where thefirst weld was formed, and when the switch next opens the weakened weld on the opposite side is broken. This operation continues during use of the switch, the contacts being opened and closed first, on one, side and thenon the other side.

While the weight 22 appears rather massivein Figs. '6 to 9, it should be remembered that these figures show the switch on. a greatly enlarged scale, and theweight 22 has a small mass and is movable by a small force. Moreover, the welds which form during operation of the switch,. as above described, are only slight welds which when weakened as described, do not prevent opening of the switch by a small force. In fact, the action involving alternate welding of the contacts on the opposite sides greatly enhances theoperation of the toaster from the standpoint of toasting the successive bread slices to the same color, as. explained below.

The thermostatic bimetal element 14 exerts a relatively slight force as it deflects in response to the rising temperature of the bread slice. Any var ation. in the load imposed on element l4 will. require a corresponding variation in the force exerted by said element before the switch contacts will open; and any variation in the exerted force will produce a variation in the color or crispness of the toasted bread, which is undesirable.

Now any switch that would be usable in conjunction with the thermostat would exhibit slight welding of the contacts during closing, because thisis inherent in any such switch. While there is a, fair degree of uniformity in the force required' to break the weld during successive openings. of the switch, the slight variations in the breaking force which must be exerted by the thermostat are adequate to produce noticeable variations in toast color on successive toasting operations. This is overcome in the present instance by virtue of the weld-weakening action thatv takes place during the operation of the switch [0, as above described. The preweakened welds require considerably less breaking force and as a result, the variations are also reduced. The smaller variations in the breaking force produce imperceptible variations. in toast color during the toasting of successive break slices.

In addition to the above results, the action of the switch distributes the contact wear evenly on; both sides, and it also minimizes the danger of switch failure due to excessive sticking of the contacts.

The foregoing results have been amply demonstrated by toasters constructed according to the present invention, and are not merely theoretical.

Referring now to Fig. 10, the mechanism of thetoaster for latching and releasing the bread carriage may be of the character disclosed in United States Patent No. 2,301,070 issued November 3, 1942to, J. W. Myers. The end plate 42' of the toaster, carries a. lever 43 which is supported on a fulcrum car 44 struck-out from said plate. A heat expansible wire 45 is looped about an insulating saddle 46 on one end of said lever, and the ends of said wire are secured to terminals 41 and 48. The bread carriage includes a plate 49 which is slidable on a vertical rod 50, and the bread carriage is urged upwardly by a spring 5|. The carriage is moved downwardly against the; action, of said springby means of a knob. 52. At the bottom of theplate 49 there, is an extending finger 53 which isengageable by alatch member 54 pivotally mounted at55. A leaf spring 56 urges the latch member toward its effective position. An arm 51 is freely carriedv atthe end of lever 43 and is urged downwardly and forwardly by a spring 58.

adapted to engage teeth 60 on the latch member 54.

When the bread carriage is raised, the; finger 53 engages arm 51 so as to disengage the pawl 59 from the latch member 54, permitting the latter to assume its normal position. When thebread carriage is lowered, it. is latched by the engagement of member 54 with finger 53. The expansible wire 45 is included in the. electric circuit of thetoaster, e. g. in series with the heat--. ingv elementsv and. theswitch l6, and the current flowing through said wire causes it to. expand. The, cessation of current fiow at the end of the toasting operation causes the wire 45, to cool and contract. Since the pawl 59 is in engagement with the teeth 60, the contraction of wire 45 effects slight upward movement of arm, 51 through lever 43, thus tripping the latch member 54 and releasing the bread carriage which is moved upwardly by the spring 5|.

Whenthe bread carriage is in its raised position, the switch It] is held open by the mechanism shown inFig. 11. A U-shaped lever 6| is pivotally supported at its ends on the depending wall? 12' of'plate H, and said lever is urged upwardly: by a spring 62. The lever 6| carries a rod 63, one end of which is adapted to engage the resilient finger 42 on lever 38. The other end of rod 63 extends upwardly and is bent to form a finger 64 carrying a roller 65. The latter is disposed in thepath of travel of the bread carriage, as shown in Fig. 10.

When the bread carriage is in raised position, the rod 63 is moved upwardly under the influence of spring 62 and engages finger 42, holding. the switch 10 open through the medium of lever 38. When the bread carriage is lowered, it engages finger 64 and depresses the rod 63 causing the latter to be moved'out of engagement with lever 38. The switch I0 is then permitted to close. under the influence of gravity.

When the switch is opened by thethermostat as above described; the latch 54 is tripped and The switch is then and by the thermostat through the associated elements. The one switch serves both to close the toaster circuit when the bread carriage is lowered, and to open the circuit and cause release. of the bread carriage when the toasting operation is finished.

As above mentioned, the thermostat and the switch cooperatively assure efficient operation of the toaster to the end that successive bread slices will be toasted to the desired color. The thermostat is truly responsive tothe surface temperature of the bread and is not appreciably affected by other factors or conditions. The switch, when closed, has only the force of gravity acting on its contacts. Hence the contact pressure is always constant. Moreover, the switch is simple and rugged, and it has the desirable operating characteristics hereinbefore described.

From the foregoing description, it will be seen At. its lower end the arm 51 carries a pawl 59 which is.

that the invention hasprovideda novel andef ficient toaster. vIt will be understood, of course, that the invention is not limited to the specific structure illustrated but is capable of various modifications. While the toaster illustrated and described has no provision for adjustment togive difierent degrees of toasting, this may easily be embodied, e. g. by movably supporting the switch and providing manually adjustable means for varying the position of the switch in relation to the wire [6.

We claim: 7

1. In a bread toaster, means defining a vertical bread slice-receiving well, heating means including heating elements disposed on opposite sides,

of said well, a generally vertical rigid support mounted between said well and one of said heating elements, a generally vertical'thermomotive element arranged to beprimarily thermally-responsive to the surface temperature of a, bread slice .in said well, said element having its upper end loosely secured to said support, and ,a compensating thermomotive element rigidly attached to said support and pivotally. connected to said first element, and arranged tobe thermally-responsive bothto said-heating means and the air temperature within the toaster.

2. In a bread toaster, means defining'a vertical bread slice-receiving well,,heating means including heating elements disposed onopposite sides of said well, agenerally vertical-rigid support; mounted between said well and one of said heating, elements, a generally vertical thermomotive element. arrangedto be primarily, thermany-responsive to the surface temperature of a bread slice in said well, said element having "its upper end loosely secured to said support, and a compensating generally vertical thermo-motive element having its lower end rigidly attached to said support and its upper end pivotally connected to said first element, and arranged to be thermally-responsive both to said heating means and the air temperature within thetoaster.

3. In a bread toaster, means defining a vertical bread slice-receiving well, heating means including heating elements disposed, on opposite sides of said well, a generally verticalrigid support mounted between said well and one of said heating elements, a generally vertical thermomotive element arranged to-be primarily thermally-responsive to the surface temperature of a bread slice in said ,well, said elementhaying its upper end loosely secured to said support, ;a compensating generally vertical thermo-motive element havingits lower end rigidly attached-to said support and its upper end pivotally con-, nected to saidfirst element, and arranged to be thermally-responsive both'to said heating means andtheair temperature within the toaster, and

a heat shield for said compensating element mounted for movement therewith vandinterposed between the bread well and said. second element.

,4. In a bread toaster, means defining avertical bread slice-receiving well, heating meansineluding heating elements disposed on opposite.

sides of said .well, a generallyvertical rigid support mounted between said well and one of said heating elements, a generally vertical thermo-r 8 motive element arranged to be primarily ther many-responsive to the surface temperature of a bread slice in said well, said element having its upper end loosely secured to said support, a compensating generally vertical thermo-motive element having its lower end rigidly attached to said support and its upper end pivotally connected to said first element, and arranged to be thermally-responsive both'to said heating means and the air temperature within the toaster, and a channel-shaped heat shield for said compensating element mounted for ,movement there with and arranged in partially surrounding relation to said compensating element to shield the latter from the surface temperature of, said bread slice.

5. In a bread toaster, means defining a bread slice receiving well, heating means including heating elements disposed on opposite sides of said well, a support member, a thermo-motive element having one of. its ends loosely secured to said support memberand positionedata side of said well so as to be primarily responsive to the surface temperature of abread slice in said well, and a compensating thermo-motive element rigidly attached to said support member and pivotally connected, tojsaid first element, and arranged to be thermally responsive both to said heating means and the air temperature within the toaster.

6. In a bread toaster, means defining a bread slice receiving well, heating means including heating elements disposed on opposite sides of said well, a support member, a thermoemotive element having one, of its ends, loosely secured to said support member and arranged to be primarily responsive tothe surface temperature of a bread slice in said' well, a compensating ther- Inc-motive element rigidly .attachedto said sup port member and pivotally connected to said first element, and arranged to be thermally responsive both to said heating means and the airtemperature within the toasten and a heatshield for said compensating element mounted for movement therewith and interposed between the bread well and said compensating element. I

ROBERT O. STEVENSON. CHARLESR. TURNER,

' aprnannoss orrnn The following references are of record in the file oi this patent: 5

UNITED STATES PA'IENTS 

